Chemistry of the Great Big Blue: A Pesticide Mystery

As part of my ongoing community-based research on water quality in coastal North Carolina, I ended up tasked with answering what I thought would be a very basic question: what is the predominant pesticide used in my county? The largest farm and by far the largest amount of cropland is occupied by a traditional corn/soy rotation with the occasional cotton thrown in. Given the multitude of American acres donated to corn/soy, I figured I could easily find out the basics of that crop’s chemistry. Not so. My little information adventure has made me realize why there are so many rumors surrounding farming’s impact on water quality in the region. Rumors are easier to find than facts.

My first stop was the agricultural extension office for the county, which is tasked with providing advice for farmers tailored to our county’s sandy coastal climate. They theoretically would know what most farmers here use as fertilizer and pesticide, at least as an anecdotal measure. Response to my question? “I personally could not begin to fathom a guess that would be any more than that: a wild guess”. She did offer to help find more information, however, as my search continued.

Stop two was the NC Department of Agriculture and Consumer Services Structural Pest Control and Pesticides Division. I received in return a hearty “good luck” along with the note that the Division does not maintain use data. He forwarded my question along to someone at the NC Field Office of the USDA National Agriculture Statistics Service (NASS). They responded that the NASS keeps such data for fruits and vegetables but not for corn or soybeans. Since most corn and soy is grown for animal feed, I’m guessing the recordkeeping requirements are less stringent.

I then remembered something about the EPA having responsibility for registering all used pesticides, so I located two nested useful programs: EPA Office of Pesticide Programs and Field Pesticide Program. They keep track of pesticide industry sales and use, as declared on their website:

EPA is responsible for regulating the production and use of pesticides in the U.S. under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Starting in 1979, EPA’s Pesticide Program has issued reports that provide economic profile information on the pesticide producing and pesticide using sectors covered by the FIFRA mandated regulatory programs. The reports contain contemporary and historical data estimating the dollar values and quantities of active ingredients used and sold in the United States.

They boast data from 2007 and earlier, much of it sourced from USDA’s NASS. Here I found a few useful pieces of aggregate information. The top three most commonly used pesticides in the country have remained the same from 2001 to 2007, so it’s a good bet that they still reign chemical king. The first, glyphosate, is the commonly vilified RoundUp used with paired RoundUp ready corn and soy. It’s an herbicide meant to kill everything but the crop in the field. The second, atrazine, is another commonly vilified herbicide perhaps best known for creating 5-legged and hermaphroditic frogs. The third is the first fumigant – metam sodium. I was not so familiar with this one, but a quick Googling informed me through the manufacturer that it’s a broad-spectrum soil fumigant applied through irrigation or injection wells. On a side note, the top search result was www.pesticideinfo.org, containing a plethora of information about the regulation and toxicity worldwide for metam sodium along with all other registered pesticides. The fourth has been climbing the list steadily for the last decade so deserves a word of mention as well: metolachlor-S, which is a targeted herbicide known for low risk of developing resistance and is integrated in “conservation tillage” practices, especially in maize fields (see recent paper). Still not exactly locally-tailored information.

Back to the notion of registering pesticides – under FIFRA, pesticides must be tracked. So there must be a pile of data somewhere that might help my quest for information. On the EPA website, I found the Pesticide Product Information System that offered a bunch of highly coded text files that could piece together the commodity chain of a particular pesticide from manufacturer to sale at the local farm supply store. With separate files for code definitions and each step of the process, this plethora of information wasn’t really helpful in answering my question. It would, at the very least, require I know where the farmers around here buy their pesticides. Since there is no farm supply store in the county that caters to commercial sales, many of these purchases may be made online or in a neighboring county. Therefore, I don’t know where to begin plowing through the offered information. The state offers a more reader-friendly website with FIFRA data, but nothing to help with my location-specific question.

My story ends with good old small-town networking. Though I was unable to get quantitative information on what chemicals are floating around my county, a number of farm operators were happy to share their chemical use practices with me and my collaborators. One was even very straightforward about which chemicals may cause the most environmental or health impacts and which would serve the purpose of our study well as indicators. The answer? Karate is most harmful to the environment; it is used as an insecticide in small quantities when pest outbreaks occur. The best indicator and most often applied are the herbicides glyphosate and 2-4-D which are applied pre-seeding and re-applied on established plants. There’s a level of trust needed to obtain this information (which may result in some protest) that is established over years of people living peaceably in the same community and seeing eye-to-eye on issues such as economic development, support of local schools, and even other environmental initiatives.